January 2024

Researchers at Newcastle University, National University of Singapore (NUS) and Japan's National Institute for Materials Science have reported on the highly anisotropic spin transport nature of two-dimensional black phosphorus.

In contrast to the conventional movement of charge in electronic devices, spintronics focuses on pioneering devices that manipulate the intrinsic property of electrons known as "spin." Similar to charges in electrons, spin gives electrons a rotational quality like they are rotating around an axis, making them behave like tiny magnets, which have both a magnitude and a direction. The electron spin can exist in one of two states, referred to as spin "up" or spin "down." This is analogous to clockwise or anticlockwise rotation. While traditional electronic devices work by moving charges around the circuit, spintronics operates by manipulating the electron spin. This is important because moving electrical charges around traditional electric circuits necessarily causes some power to be lost as heat, whereas the motion of spin does not intrinsically dissipate as much heat. This characteristic could potentially allow for lower-power device operation.

Higher-order topological insulators, or HOTIs, have attracted attention for their ability to conduct electricity along one-dimensional lines on their surfaces, but this property is quite difficult to experimentally distinguish from other effects. 

By instead studying the interiors of these materials from a different perspective, a team of researchers at the University of Illinois at Urbana-Champaign, Dublin Institute for Advanced Studies, Chinese Academy of Sciences and additional collaborators has identified a surface signature that is unique to HOTIs that can determine how light reflects from their surfaces. 

Researchers at the National Synchrotron Light Source II at Brookhaven National Laboratory, University of California Davis, University of Colorado Springs, Stockholm University, National Institute of Standards and Technology, University of California San Diego, Ca’ Foscari University of Venice, and Elettra Sincrotrone Trieste have conducted an experiment with magnetic materials and ultrafast lasers that could advance energy-efficient data storage.

"We wanted to study the physics of light-magnet interaction," said Rahul Jangid, who led the data analysis for the project while earning his Ph.D. in materials science and engineering at UC Davis under associate professor Roopali Kukreja. "What happens when you hit a magnetic domain with very short pulses of laser light?"

Researchers at Japan's RIKEN have conducted an experiment that could help the development of new energy-efficient spintronics devices. They used heat and magnetic fields to create transformations between spin textures—magnetic vortices and antivortices known as skyrmions and antiskyrmions—in a single crystal thin plate device. What's even more important is that they achieved this at room temperature.

Skyrmions and antiskyrmions, which are textures that exist within special magnetic materials involving the spin of the electrons in the material, are an active area of research, as they could be used for next-generation memory devices, for example, with skyrmions acting as a "1" bit and antiskyrmions a "0" bit. In the past, scientists have been able to move them in a variety of ways, and to create transformations between them using electric current. However, because current electronic devices consume electrical power and produce waste heat, the researchers in the group, led by Xiuzhen Yu at the RIKEN Center for Emergent Matter Science, decided to see if they could find a way to create the transformations using heat gradients.

A Japanese research team, led by Jun Okabayashi from the University of Tokyo, including Associate Professor Yoshihiro Gohda from Tokyo Tech and Osaka University researchers, recently revealed a strain-induced orbital control mechanism in interfacial multiferroics. 

Controlling the direction of magnetization using low electric field is important for achieving efficient spintronic devices. In spintronics, properties of an electron's spin or magnetic moment are used to store information. The electron spins can be manipulated by straining orbital magnetic moments to create a high-performance magnetoelectric effect.

Researchers at Japan's Tokyo Institute of Technology (Tokyo Tech) have demonstrate the concept of Berry phase monopole engineering of the spin Hall effect in non-centrosymmetric silicide TaSi₂.

Image credit: Tokyo Tech

Spin-transfer torque is an important phenomenon that enables ultrafast and low-power spintronic devices. Recently, however, spin-orbit torque (SOT) has emerged as a promising alternative to spin-transfer torque. Many studies have investigated the origin of SOT, showing that in non-magnetic materials, a phenomenon called the spin Hall effect (SHE) is key to achieving SOT. In these materials, the existence of a “Dirac band” structure, a specific arrangement of electrons in terms of their energy, is important to achieving large SHE. This is because the Dirac band structure contains “hot spots” for the Berry phase, a quantum phase factor responsible for the intrinsic SHE. Thus, materials with suitable Berry phase hot spots are key to engineering the SHE.